This invention relates to printing mechanisms and, in particular, to page wide array printbars and wiper assemblies.
An inkjet printer includes a printing assembly having a printhead, or printheads, to deposit ink onto a print media, such as paper. A printhead has an orifice plate that is formed with nozzles through which ink drops are xe2x80x9cfiredxe2x80x9d, or otherwise ejected, onto the print media to form an image, such as text or a picture. The ink drops dry, or are heated to dry, on the print media shortly after deposition to form the printed image.
There are various types of inkjet printheads including, for example, thermal inkjet printheads and piezoelectric inkjet printheads. For a thermal inkjet printhead, ink droplets are ejected from individual nozzles by localized heating with a heating element located at individual nozzles. An electric current is applied to a heating element to heat it up which causes a small volume of ink to be rapidly heated and vaporized. Once vaporized, the ink is ejected through the nozzle. A driver circuit is coupled to individual heating elements to provide the energy pulses and thereby controllably deposit ink drops from associated individual nozzles. The drivers are responsive to character generators and other image forming circuitry to energize selected nozzles of a printhead for forming images on the print media.
During printing, ink tends to build up at the nozzle orifices of a printhead. This build-up of residual ink can be caused by ink droplets that are not completely ejected from a nozzle, excess ink at the orifice that is not fully vaporized, or ink spatterings that reflect from the print media when the ink is ejected. The small nozzle orifices of a printhead are also susceptible to clogging by quick drying ink, dust particles and paper fibers, and from solids within the ink. Partially or completely blocked nozzles can result in either missing or misdirected ink drops being deposited onto the print media, either of which impairs printing and degrades the print quality.
The printing assembly typically includes a service station having wipers to clean and preserve the functionality of the printheads. The service station includes a wiper, or wipers, for wiping a printhead to remove ink residue and other contaminants that have been deposited or collected on the printhead surface and over the nozzle openings in the printhead surface. A service station can also include a cap, or capping mechanism, which covers a printhead when the printer is not printing to prevent the ink in the nozzles from drying, and to prevent contaminants from collecting in and over the nozzles.
A conventional inkjet printer has a print unit that includes a reciprocating inkjet pen carriage system for travel back and forth across a print zone along an axis that spans a print media, or otherwise spans a printing width. A conventional print unit also includes a service station fixed within the inkjet printer away from the print zone. To service the printhead nozzles of the inkjet pen carriage system, the carriage system travels along the axis and away from the print zone, or outside of the print zone, to the service station.
With the advent of page wide array printbar assemblies having multiple printheads that span the width of a print media, or otherwise span a printing width, there is a need for improved printing mechanisms having printbar assemblies that are accessible to clean the multiple printheads, and service station assemblies that move wipers and printhead caps to the printheads, rather than the printheads being moved to the wipers at a service station.
A print unit, such as an inkjet printing mechanism, includes a printbar assembly that has print modules with one or more printheads to deposit an imaging medium, such as ink, onto a print media. The one or more printheads of the print modules collectively span a width of a print media, or print region, when the printbar assembly is in a print position.
The print unit also includes a service station having a wiper assembly with one or more wipers that correspond to the one or more printheads on the printbar assembly, such that when a wiper assembly and a printbar assembly are positioned in proximity to service the printheads, the wipers clean the printheads of ink residue and contaminants.
The wiper assembly moves from a print position to a service position within the print region to service the one or more printheads on the printbar assembly. In addition to having one or more wipers, the wiper assembly has one or more printhead caps that cover the one or more printheads on the printbar assembly.